Is it possible to write swap method in Java?

Question

Here is the question: write a method that swaps two variables. These two variables should be primitives. It doesn't need to be generic e.g. two int variables. Is there a way?!

Answer 1

Without using an array or objects, no, it is not possible to do it within a method.

Answer 2

Check out this JavaWorld article that explains it in detail:

http://www.javaworld.com/javaworld/javaqa/2000-05/03-qa-0526-pass.html

A swap of two primitives will never work because primitives are passed by value in Java. You can't even write a method to swap two objects for that matter.

Like @Thomas said, the only thing you could do is have your primitives contained within other objects/arrays and modify those.

Answer 3

In java5, the closest I can think of, which may help you, is :

The AtomicInteger class (and others) have getAndSet() atomic methods ..

Answer 4

As Thomas Owens said. You could probably do it in C by passing variables by &reference, but afaik not in Java without using objects.

Answer 5

To write a swap method that swaps primitives you'd have to have the concept of "out" variables, i.e. variables whose values are passed up to the calling context. C# has those but you must still specify that they're out variables.

Answer 6

You can write method which will return two-elements array which contents are swapped parameters to that method.

static Object[] swap(Object a, Object b) {
    return new Object[]{b,a};
}